An exhaust gas treatment system may be included in an exhaust system of an engine in a vehicle in order to reduce regulated emissions. In one example, the exhaust gas treatment system may include a diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC). An exhaust gas temperature may be increased periodically in order to burn accumulated soot in the DPF in a process known as DPF regeneration. During some conditions, such as extended cold idling, unburned hydrocarbons from the engine may accumulate in the exhaust gas treatment system and may be unaccounted for. During a subsequent DPF regeneration, the accumulated unburned hydrocarbons may burn rapidly. Exothermic heat from the burning hydrocarbons is uncontrolled and un-metered, resulting in excessively high temperatures in the exhaust system which may lead to degradation of the DPF and/or DOC.
The inventors herein have recognized the above issue and have devised an approach to at least partially address it. Thus, a method for an exhaust system is disclosed. The method includes, in response to extended cold idle operation, and in response to a particulate filter regeneration request, first removing hydrocarbons stored in the particulate filter, and then performing the particulate filter regeneration.
In one example, an exhaust gas temperature may be increased to a first temperature, but less than a second temperature, in order to remove the hydrocarbons by desorbing them, and then further increased to the second temperature to initiate regeneration of the particulate filter. A duration the exhaust gas remains at the first temperature may be based on duration of the extended cold idle operation and the exhaust temperature during the idle operation, for example. By removing the hydrocarbons before performing the particulate filter regeneration, degradation of the particulate filter due to burning of the hydrocarbons may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.